Only yesterday we were complaining that the Palm Centro didn't have enough oomph for our liking when--whaddaya know?--the postman kindly delivered Garmin's Mobile 10, a memory card and sat-nav receiver combo that converts a variety of smartphones, including the Centro, into satellite navigation devices.

You simply stick the card--in microSD, miniSD, and SD formats, all included--into your smartphone, and the sat-nav software automatically starts to install itself. Once installed, you're ready to go and can input full addresses or just a zip code. The receiver automatically pairs with your phone via Bluetooth when you launch the app. If your phone has a GPS receiver built in, you can buy the card separately, as the Garmin Mobile XT.

Similar to a standalone sat-nav you get directions read out over your phone's speaker and a 3D map view. It'll re-route you if you go the wrong way by mistake and it'll even offer real-time traffic alerts for no extra cost. Our only niggle with it is that it doesn't read out street names.

Garmin Mobile XT costs around 60 pounds (about $121) and is designed for phones that already have GPS, such as the Nokia N95 or HTC TyTN II. Garmin Mobile 10 costs around 100 pounds (about $202) and is designed for smart phones that don't have GPS built in, such as the Palm Centro or Nokia N73.